Transmissions for vehicles having a combustion engine are protected by an interface that limits the input torque to the transmission. In some hybrid vehicles a combustion engine and an electric machine, or motor/generator, are both available for torque production and are separable by a disconnect clutch. The sum of the torque provided by the combustion engine and an electric machine is transmitted to the input of the transmission through a launch clutch. The launch clutch must be rated to hold the torque from the engine and the electric machine, including inertia torques.
Transmission interfaces are available that limit the torque to the input of the transmission to protect a launch clutch that connects the torque producer, for example a combustion engine, to the transmission. These transmission interfaces do not limit the engine torque separately from the electric machine torque in a hybrid vehicle powertrain that has more than one source of torque. As a result, the disconnect clutch is unprotected by use of current transmission interfaces. To compensate for the lack of protection, the system controller may be required to reduce the total input torque below driver demand to protect the disconnect clutch from excessive torque loads.
This disclosure focuses on the above problem and other problems relating to the protection of the disconnect clutch from excessive torque.